A defiant Turkish President Tayyip Erdogan denounced the West's "crusader mentality" on Monday after European monitors criticized a referendum to grant him sweeping new powers, which he won with a narrow victory laying bare the nation's divisions.
Supporters thronged the streets honking horns and waving flags, while opponents banged pots and pans in protest in their homes into the early morning. The main opposition party rejected the result and called for the vote to be annulled.
Election authorities said preliminary results showed 51.4 percent of voters had backed the biggest overhaul of Turkish politics since the founding of the modern republic.
Erdogan says concentrating power in the hands of the president is vital to prevent instability. But the narrowness of his victory could have the opposite effect: adding to volatility in a country that has lately survived an attempted coup, attacks by Islamists, a Kurdish insurgency, civil unrest and war across its Syrian border.
The result laid bare the deep divide between the urban middle classes who see their future as part of a European mainstream, and the pious rural poor who favor Erdogan's strong hand. Erdogan made clear his intention to steer the country away from Europe, announcing plans to seek to restore the death penalty, which would effectively end Turkey's decades-long quest to join the EU.
"The crusader mentality in the West and its servants at home have attacked us," he told flag-waving supporters on arrival in the capital Ankara where he was due to chair a cabinet meeting, in response to the monitors' assessment.
In the bluntest criticism of a Turkish election by European monitors in memory, a mission of observers from the 47-member Council of Europe, the continent's leading human rights body, said the referendum was an uneven contest. Support for a "Yes" vote dominated campaign coverage, and the arrests of journalists and closure of media outlets prevented other views from being heard, the monitors said.
"In general, the referendum did not live up to Council of Europe standards. The legal framework was inadequate for the holding of a genuinely democratic process," said Cezar Florin Preda, head of the delegation.
While the monitors had no information of actual fraud, a last-minute decision by electoral authorities to allow unstamped ballots to be counted undermined an important safeguard and contradicted electoral law, they said.
The bitter campaigning and narrow "Yes" vote exposed deep divisions in Turkey, with the country's three main cities and mainly Kurdish southeast likely to have voted "No". Official results are due to be announced in the next 12 days.
Erdogan, a populist with a background in once-banned Islamist parties, has ruled since 2003 with no real rival, while his country emerged as one of the fastest-growing industrial powers in both Europe and the Middle East.
He has also been at the center of global affairs, commanding NATO's second-biggest military on the border of Middle East war zones, taking in millions of Syrian refugees and controlling their further flow into Europe.
Critics accuse him of steering Turkey towards one-man rule. The two largest opposition parties both challenged Sunday's referendum, saying it was deeply flawed.
The pro-Kurdish opposition Peoples' Democratic Party said it presented complaints about unstamped ballots affecting 3 million voters, more than twice the margin of Erdogan's victory.
The main secularist opposition People's Republican Party said it was still unclear how many votes were affected.
"This is why the only decision that will end debate about the legitimacy (of the vote) and ease the people's legal concerns is the annulment of this election," deputy party chairman Bulent Tezcan said.
Tezcan said he would if necessary go to Turkey's constitutional court - one of the institutions that Erdogan would gain firm control over under the constitutional changes, through the appointment of its members.
The president survived a coup attempt last year and responded with a crackdown, jailing 47,000 people and sacking or suspending more than 120,000 from government jobs such as schoolteachers, soldiers, police, judges or other professionals.
The changes could keep him in power until 2029 or beyond, making him easily the most important figure in Turkish history since state founder Mustafa Kemal Ataturk built a modern nation from the ashes of the Ottoman empire after World War One.
Germany, host to some 4 million Turks, said it was up to Erdogan himself to heal the rifts that the vote had exposed.
"The tight referendum result shows how deeply divided Turkish society is, and that means a big responsibility for the Turkish leadership and for President Erdogan personally," said Chancellor Angela Merkel and Foreign Minister Sigmar Gabriel in a joint statement.
Relations with Europe were strained during the referendum campaign when Germany and the Netherlands barred Turkish ministers from holding rallies. Erdogan provoked a stern German response by comparing those limits to the actions of the Nazis.
Thousands of Erdogan supporters waved flags and blasted horns into the early hours on Monday in celebration of a man who they say has transformed the quality of life for millions of pious Turks marginalized for decades by the secular elite.
There were scattered protests against the result, but these were more sporadic. In some affluent, secular neighborhoods, opponents stayed indoors, banging pots and pans, a sign of dissent that became widespread during anti-Erdogan protests in 2013, when the police crushed demonstrations against him.
The result triggered a two percent rally in the Turkish lira from its close last week.
Under the changes, most of which will only come into effect after the next elections due in 2019, the president will appoint the cabinet and an undefined number of vice-presidents, and be able to select and remove senior civil servants without parliamentary approval.
There has been some speculation that Erdogan could call new elections so that his new powers could take effect right away. However, Deputy Prime Minister Mehmet Simsek told Reuters there was no such plan, and the elections would still be held in 2019.
Erdogan served as prime minister from 2003 until 2014, when rules were changed to hold direct elections for the office of president, previously a ceremonial role elected by parliament. Since becoming the first directly elected president, he has set about making the post more important, along the lines of the executive presidencies of France, Russia or the United States.